arXiv subjects

F. Michel Dekking

Publications and source records attributed to F. Michel Dekking.

7 recordsLinked to original sources

arXiv2023

The structure of base phi expansions

In the base phi expansion any natural number is written uniquely as a sum of powers of the golden mean with coefficients 0 and 1, where it is required that the product of two consecutive digits is always 0. We tackle the problem of describing how these expansions look like. We classify the positive parts of the base phi expansions according to their suffices, and the negative parts according to their prefixes, specifying the sequences of occurrences of these digit blocks. Here the situation is much more complex than for the Zeckendorf expansions, where any natural number is written uniquely as a sum of Fibonacci numbers with coefficients 0 and 1, where, again, it is required that the product of two consecutive digits is always 0. In a previous work we have classified the Zeckendorf expansions according to their suffices. It turned out that if we consider the suffices as labels on the Fibonacci tree, then the numbers with a given suffix in their Zeckendorf expansion appear as generalized Beatty sequences in a natural way on this tree. We prove that the positive parts of the base phi expansions are a subsequence of the sequence of Zeckendorf expansions, giving an explicit formula in terms of a generalized Beatty sequence. The negative parts of the base phi expansions no longer appear lexicographically. We prove that all allowed digit blocks appear, and determine the order in which they do appear.

math.NT↗

arXiv2021

Sumsets and fixed points of substitutions

In this paper we introduce a technique to determine the sumset $A+A$, where $A$ is the indicator function of the 0's occurring in a fixed point $x$ of a substitution on the alphabet $\{0,1\}$.

math.CO↗

arXiv2020

How to add two natural numbers in base phi

In the base phi representation any natural number is written uniquely as a sum of powers of the golden mean with coefficients 0 and 1, where it is required that the product of two consecutive digits is always 0. In this self-contained paper we give a new, and short proof of the recursive structure of the base phi representations of the natural numbers.

math.NT↗

arXiv2019

Queens in exile: non-attacking queens on infinite chess boards

Number the cells of a (possibly infinite) chessboard in some way with the numbers 0, 1, 2, ... Consider the cells in order, placing a queen in a cell if and only if it would not attack any earlier queen. The problem is to determine the positions of the queens. We study the problem for a doubly-infinite chessboard of size Z x Z numbered along a square spiral, and an infinite single-quadrant chessboard (of size N x N) numbered along antidiagonals. We give a fairly complete solution in the first case, based on the Tribonacci word. There are connections with combinatorial games.

math.CO↗

arXiv2016

Morphisms, Symbolic sequences, and their Standard Forms

Morphisms are homomorphisms under the concatenation operation of the set of words over a finite set. Changing the elements of the finite set does not essentially change the morphism. We propose a way to select a unique representing member out of all these morphisms. This has applications to the classification of the shift dynamical systems generated by morphisms. In a similar way, we propose the selection of a representing sequence out of the class of symbolic sequences over an alphabet of fixed cardinality. Both methods are useful for the storing of symbolic sequences in databases, like The On-Line Encyclopedia of Integer Sequences. We illustrate our proposals with the $k$-symbol Fibonacci sequences.

math.CO↗

arXiv2015

Topological conjugacy of constant length substitution dynamical systems

Primitive constant length substitutions generate minimal symbolic dynamical systems. In this article we present an algorithm which can produce the list of injective substitutions of the same length that generate topologically conjugate systems. We show that each conjugacy class contains infinitely substitutions which are not injective. As examples, the Toeplitz conjugacy class contains three injective substitutions (two on two symbols and one on three symbols), and the length two Thue-Morse conjugacy class contains twelve substitutions, among which are two on six symbols. Together, they constitute a list of all primitive substitutions of length two with infinite minimal systems which are factors of the Thue-Morse system.

math.DS↗

arXiv2008

Differences of random Cantor sets and lower spectral radii

We investigate the question under which conditions the algebraic difference between two independent random Cantor sets $C_1$ and $C_2$ almost surely contains an interval, and when not. The natural condition is whether the sum $d_1+d_2$ of the Hausdorff dimensions of the sets is smaller (no interval) or larger (an interval) than 1. Palis conjectured that \emph{generically} it should be true that $d_1+d_2>1$ should imply that $C_1-C_2$ contains an interval. We prove that for 2-adic random Cantor sets generated by a vector of probabilities $(p_0,p_1)$ the interior of the region where the Palis conjecture does not hold is given by those $p_0,p_1$ which satisfy $p_0+p_1>\sqrt{2}$ and $p_0p_1(1+p_0^2+p_1^2)<1$. We furthermore prove a general result which characterizes the interval/no interval property in terms of the lower spectral radius of a set of $2\times 2$ matrices.

math.PR↗